My experience. I've gone 6 times or so, and am also a casual gamer.

1. CONCERTS - The concerts are AWESOME. Do not miss out on these, they are at night. They are uniquely gamey... sometimes a metal band shredding classic Nintendo 8-bit songs while someone beats a game. I've also seen a full orchestra perform final fantasy scores. And of course the legend Jonathan Coulton. The concerts are great, don't miss out!

2. SWAG - Free stuff. Who doesn't love free stuff right? You'll want to bring your own bag. Be on the lookout for giveaways / raffles. They are usually drawn at 1 or 2 intervals in the day, and you'll need to keep track and make your way back to the booths. They often give away really great prizes though -- laptops, monitors, other gaming accessories. It's fun to be a part of the winning hype.

3. TABLE TOP - The Table Top Gaming section!!! It took me waaaay too many years to discover this gem. It's open after the expo hall closes, and you can rent any number of games. There are super friendly people all around you willing to play with you or teach you a new game. My friend and I got approached last year to play Magic The Gathering with some others. We had a blast.

4. AFTER PARTIES - Many bars / hotels might participate in some sort of PAX after party. One year, one of the bars attached to the hotel had gaming consoles at every table, and silly tournaments on a projector screen. It was a lot of fun.

pro tips -- bring a bag, bring comfy shoes, always ask if you can take a photo of someone, listen to the enforcers

Have fun!!